Regarding the excess bulk on the ends I can verify that using Speedmaster heads on a 78 Magnum with 360 and A/C using factory brackets and original square back alternator we could not get the alternator back on after the engine re-build with those heads. Instead of monkeying with brackets, cutting/extending and using longer belts etc we ended up fitting the small Denso for a Toyota (was a snap to fit by the way!)
The bulk is an important concern for some applications and certainly for those who don’t want to resort to modifying or butchering just to make something fit that should just fit.
